The need to provide an internal combustion engine of a motorcycle with a silencing system is well known, and, various arrangements of silencing mufflers have been proposed and are well known for this purpose.
More recently, requirements have been imposed for the incorporation of exhaust purifying devices into the exhaust systems of motorcycles, the exhaust purifying devices being constituted by catalytic or other converters which are arranged in series flow relationship with the silencing muffler.
The incorporation of a catalytic converter into the exhaust system of a motorcycle gives rise to acute problems in arranging the catalytic converter and the silencing muffler in an aesthetically pleasing manner. Additionally, in view of the limitation on the axial length of the exhaust system in a longitudinal direction of the motorcycle, acute engineering problems arise in maintaining the catalytic converter and the silencing muffler within the permitted axial length, without sacrificing efficiency of the silencing muffler in its sound attenuating capacity.